Universal terminal bar structure with ground contacting feature integrated into a body structure with versatile RFI suppression for electric motors
A method of providing RFI suppression in a DC motor provides a universal terminal bar structure 70 including a positive terminal bar 72 and a negative terminal bar 76, a first choke 80 electrically connected with the positive terminal bar, a second choke 82 electrically connected with the negative terminal bar, a first ground connection 86 constructed and arranged to electrically connect the positive terminal bar to ground, a first breakable section A between the first ground connection and the positive terminal bar, a second ground connection 88 constructed and arranged to electrically connect the negative terminal bar to ground, and a second breakable section B between the second ground connection and the negative terminal bar. Capacitor structure 90 is attached to the terminal bar structure, and the first breakable section is selectively broken, alone or in combination with the second breakable section to provide versatile RFI suppression.
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This application is based on U.S. Provisional Application No. 60/550,474, filed on Mar. 5, 2004 and claims the benefit thereof for priority purposes.
FIELD OF THE INVENTIONThe invention relates to permanent magnet direct current (DC) motors for automotive applications and, more particular, to a terminal bar structure that provides versatile RFI suppression.
BACKGROUND OF THE INVENTIONThe functionality of permanent magnet direct current brush-commutated electric motors requires switching current from winding to winding. As the brushes slide from one bar to another an arching occurs due to the back electromotive force (EMF) generated by the stored electromagnetic energy in the current carrying coils. The arching generates broadband electrical noise over a wide frequency spectrum. The spectrum energy distribution is influenced by switching of coils (commutation) that is proportional to the motor speed.
There are two modes of conducted noise generated in a motor, differential mode and common mode. The differential mode filtering can be accomplished with a shunt capacitor connected across the positive and negative motor terminals and use of series inductors or ferrite beads (chokes) to reduce radio frequency (RF) noise currents. The common mode filtering is also accomplished by including series impedance in both leads in addition to referencing the shunt capacitor and the negative terminal to case. However, the motor case and vehicle ground must be at the same potential. If the case and vehicle ground are at different potential then the RF reference can be provided by an additional capacitor. This type of filtering is shown in
Although the construction of the brush card assembly for a four-brush configuration is significantly different from the two-brush configuration, the method of assembling the capacitors and grounding to motor case for RFI suppression are the same. The attachment of capacitors 32, 48, and 62 in
Therefore, a more universal and versatile terminal bar system is needed that can be more cost effective and that can accommodate automated assembly.
SUMMARY OF THE INVENTIONAn object of the invention is to fulfill the need referred to above. In accordance with the principles of the present invention, this objective is achieved by a method of providing RFI suppression in a DC motor. The method provides a universal terminal bar structure including a positive terminal bar and a negative terminal bar, a first ground connection constructed and arranged to electrically connect the positive terminal bar to ground, a first breakable section between the first ground connection and the positive terminal bar, a second ground connection constructed and arranged to electrically connect the negative terminal bar to ground, and a second breakable section between the second ground connection and the negative terminal bar. Capacitor structure is attached to the terminal bar structure, and the first breakable section is selectively broken, alone or in combination with the second breakable section to provide versatile RFI suppression.
In accordance with another aspect of the invention, a universal terminal bar structure is provided for a permanent magnet DC motor. The structure includes a body structure, a positive terminal bar and a negative terminal bar, each being carried by the body structure, a first ground connection constructed and arranged to electrically connect the positive terminal bar to ground, a first breakable section between the first ground connection and the positive terminal bar constructed and arranged such that when the first breakable section is broken, the connection between ground and the positive terminal bar is terminated, a second ground connection constructed and arranged to electrically connect the negative terminal bar to ground, a second breakable section between the second ground connection and the negative terminal bar constructed and arranged such that when the second breakable section is broken, the connection between ground and the negative terminal bar is terminated, and capacitor structure attached to the terminal bar structure. Whereby placement of the capacitor structure and selectively breaking the first breakable section, alone or in combination with the second breakable section, provides selective radio frequency interference (RFI) suppression for the motor.
Other objects, features and characteristics of the present invention, as well as the methods of operation and the functions of the related elements of the structure, the combination of parts and economics of manufacture will become more apparent upon consideration of the following detailed description and appended claims with reference to the accompanying drawings, all of which form a part of this specification.
BRIEF DESCRIPTION OF THE DRAWINGSThe invention will be better understood from the following detailed description of the preferred embodiments thereof, taken in conjunction with the accompanying drawings, wherein like reference numerals refer to like parts, in which:
With reference to
A break-off (breakable) section encircled at A in
With the terminal bar structure 70, the following type of RFI suppressions can be achieved:
1. The Type 1 RFI suppression as shown in
2. The Type 2 RFI suppression as shown in
3. The Type 3 RFI suppression as illustrated on
Thus, breakable section A is always cut, broken or removed, and breakable section B is cut or broken only when capacitor 92 is employed. Providing the breakable sections A and B enables the terminal bars 72 and 76 to be cut out or stamped as explained above.
The capacitors are assembled, for example, by resistance welding/fusing or ultrasonic welding (however the assembly is not limited to these methods). The grommet or connector body 78 can be molded after or before the capacitors are assembled to the terminal bar structure 70. However, the positive lead wire 38 and the negative lead wire 36 need to be attached to the associated terminal bar before molding the grommet 78 around the terminal bars.
The advantage with the versatile terminal bar structure 70 is that the attachment of capacitor and ground connections can be automated. Also, the capacitors are placed on the terminal bar structure 70 based on the type and level of RFI suppression requirements. Therefore, with this structure, multiple type and levels of RFI suppression can be achieved.
Also, the same grommet or connector body structure 78 with the insert molded terminal bars can be used for one or two or even three positive power input applications. This requirement is quite common when one or two resistors are connected in series to the motor for two or three speed application. The advantage of this structure is that with the “flow through” feature 94 on the positive terminal bar 71 all positive power inputs are jointed and insert molded into the grommet or connector body 78.
Another advantage of the terminal bar structure 70 is the method of grounding to the motor case/stator assembly. This is illustrated in
Features of the invention include:
1. Integrate ground contact terminal bar into grommet or connector body structure.
2. Insert mold RFI suppression components into grommet or connector body structure.
3. Integrate FRI suppression component into grommet or connector body structure.
4. Insert mold terminal bar to grommet or connector body structure with flow through feature to accommodate for two or multiple terminal power inputs but with only two terminals to the RFI chokes or brushes.
5. A method of ground connection without grinding paint from the motor case/stator assembly.
6. Insert molded terminal bar with features such as the break-off sections that allow for a versatile RFI suppression assembly.
The foregoing preferred embodiments have been shown and described for the purposes of illustrating the structural and functional principles of the present invention, as well as illustrating the methods of employing the preferred embodiments and are subject to change without departing from such principles. Therefore, this invention includes all modifications encompassed within the spirit of the following claims.
Claims
1. A terminal bar structure for a permanent magnet DC motor, the structure comprising:
- a body structure,
- a positive terminal bar and a negative terminal bar, each being carried by the body structure,
- a first ground connection constructed and arranged to electrically connect the positive terminal bar to ground,
- a first breakable section between the first ground connection and the positive terminal bar constructed and arranged such that when the first breakable section is broken, the connection between ground and the positive terminal bar is terminated,
- a second ground connection constructed and arranged to electrically connect the negative terminal bar to ground,
- a second breakable section between the second ground connection and the negative terminal bar constructed and arranged such that when the second breakable section is broken, the connection between ground and the negative terminal bar is terminated, and
- capacitor structure attached to the terminal bar structure,
- whereby placement of the capacitor structure and selectively breaking the first breakable section, alone or in combination with the second breakable section, provides selective radio frequency interference (RFI) suppression for the motor.
2. The structure of claim 1, wherein the body structure is a grommet and at least portions of the terminal bars are insert molded in the grommet.
3. The structure of claim 1, further comprising at least one first choke electrically connected with the positive terminal bar, and at least one second choke electrically connected with the negative terminal bar.
4. The structure of claim 1, wherein the body structure is a connector body and at least portions of the terminal bars are insert molded in the connector body.
5. The structure of claim 3, wherein the positive terminal bar includes a generally Y-shaped portion defining two legs that are joined to a common member, one leg defining a terminal bar connection for a certain speed operation of the motor and the other leg defining a terminal bar connection for operation of the motor at a speed less than the certain speed.
6. The structure of claim 5, wherein the at least one positive choke is connected to the common member of the positive terminal bar.
7. The structure of claim 1, in combination with the motor, the motor having an end cap and a motor case, wherein the first and second ground connections are compressed between the end cap and the motor case such that under compression, the ground connections cut into the motor case to create ground contact.
8. The structure of claim 1, wherein the capacitor structure includes a capacitor electrically connected between the positive terminal bar and the negative terminal bar, and wherein only the first breakable section is broken.
9. The structure of claim 1, wherein the capacitor structure includes a capacitor electrically connected between the first ground connection and the positive terminal bar and another capacitor electrically connected between the positive terminal bar and the negative terminal bar, and wherein the only first breakable section is broken.
10. The structure of claim 1, wherein the capacitor structure includes a capacitor electrically connected between the first ground connection and the positive terminal bar and another capacitor electrically connected between the second ground connection and the negative terminal bar, and wherein both the first breakable section and the second breakable section are broken.
11. A method of providing RFI suppression in a DC motor including:
- providing a universal terminal bar structure comprising: a positive terminal bar and a negative terminal bar, a first ground connection constructed and arranged to electrically connect the positive terminal bar to ground, a first breakable section between the first ground connection and the positive terminal bar, a second ground connection constructed and arranged to electrically connect the negative terminal bar to ground, and a second breakable section between the second ground connection and the negative terminal bar,
- attaching capacitor structure to the terminal bar structure, and selectively breaking the first breakable section alone or in combination with the second breakable section.
12. The method of claim 11, wherein the step of attaching capacitor structure includes electrically connecting a capacitor between the positive terminal bar and the negative terminal bar.
13. The method of claim 12, wherein the step of breaking includes breaking only the first breakable section so as to terminate the connection between ground and the positive terminal bar is terminated.
14. The method of claim 11, wherein the step of attaching capacitor structure includes electrically connecting a capacitor between the first ground connection and the positive terminal bar and electrically connecting another capacitor between the positive terminal bar and the negative terminal bar.
15. The method of claim 14, wherein the step of breaking includes breaking only the first breakable section so as to terminate the connection between ground and the positive terminal bar is terminated.
16. The method of claim 11, wherein the step of attaching capacitor structure includes electrically connecting a capacitor between the first ground connection and the positive terminal bar and electrically connecting another capacitor between the second ground connection and the negative terminal bar.
17. The method of claim 16, wherein the step of breaking includes breaking both the first breakable section and the second breakable section to eliminate direct contact of the terminal bars to ground.
18. The method of claim 11, further including molding a connector body about at least a portion of the terminal bar structure.
19. The method of claim 11, further including attaching a lead wire to the positive terminal bar and attaching another lead wire to the negative terminal bar and thereafter, molding a connector body about at least a portion of the terminal bar structure.
20. The method of claim 11, further including electrically connecting at least one first choke with the positive terminal bar and electrically connecting at least one second choke with the negative terminal bar.
21. The method of claim 11, wherein the motor includes an end cap and a motor case, the method further including compressing the first and second ground connections between the end cap and motor case such that under compression, the ground connections cut into the motor case to create ground contact.
22. The method of claim 11, wherein the step of providing the terminal bar structure includes providing the terminal bar structure as a single piece and then separating the positive terminal bar from the negative terminal bar.
Type: Application
Filed: Mar 2, 2005
Publication Date: Sep 8, 2005
Patent Grant number: 7291957
Applicant:
Inventors: Attila Simofi-Ilyes (London), Stefan Smorowski (London), Steven VanHorne (St. Thomas), Rod VanWyck (London), Andrew Lakerdas (London)
Application Number: 11/070,174